This animation shows how the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) instrument on LRO works. It starts with a wide view of the LRO spacecraft with cosmic rays buzzing by around it then graduallly pushes in on the CRaTER instrument. We see a cutaway of the instrument as a cosmic ray enters the telescope and passes through layers of tissue-equivalent plastics with sensors laid in between.

By detecting the amounts, types, and sources of radiation passing through medical-grade tissue equivalent plastics, CRaTER gives researchers an idea of what risks a human in the lunar environment might encounter. This image shows the animated cutaway of the instrument and points out what the different parts are.